Public sector pay growth is now outpacing the private sector by one-third as Rachel Reeves struggles to get spending under control ahead of the Budget.
Increased spending on doctors and teachers means pay in the public sector surged by 6pc in September, more than one-third faster than a 4.4pc increase in the private sector, according to figures from jobs site Adzuna.
The figures will increase pressure on the Chancellor as she seeks to scale back public spending in the run up to her November 26 Budget.
Ms Reeves must plug a £30bn black hole in the public finances after UK borrowing hit its highest level in five years in September but faces a challenge to cut down the public sector wage bill.
Adzuna said the large rise in public sector pay reflected efforts by the NHS and schools to fill vital roles amid persistent strike action by doctors and a lack of applicants for teaching roles.
Because there are more vacancies than candidates, the public sector must pay more to fill the roles, leading to higher wage growth.
Last week the British Medical Association announced another round of strikes from junior doctors in November, which will be the 13th strike since March 2023.
It comes as Adzuna's data shows that job vacancies in Britain hit their lowest point this year in September as businesses pause hiring ahead of the Budget.
Increases to the National Minimum Wage as well as hikes to employers' National Insurance Contributions have already increased costs for businesses.
Upcoming workers' rights laws - the biggest overhaul of employee rights in a generation - are also set to further complicate hiring and firing decisions.
The ONS estimates that 15,000 working days were lost because of labour disputes across the UK in August alone.
On Monday, the British Chamber of Commerce (BCC) also urged the Government to address Britain's private sector hiring slump.
According to a poll of businesses by the BCC, 75pc say they continue to face recruitment challenges, with only a fifth increasing their workforces in the third quarter.
They say that businesses are "just about coping", but with the tax rises they are not investing and cannot afford to hire new staff.
Jane Gratton, from the BCC, said: "Unless more is done to boost access to skills and contain employment costs, economic growth will remain stunted."